1. Field of the Invention
This invention relates generally to semiconductor manufacturing, and, more particularly, to a method and apparatus for determining a desirable mixture of integrated and off-line metrology data perform process control.
2. Description of the Invention
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today""s manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (deposition, etching, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing areas or locations that contain different control schemes.
Generally, a set of processing steps is performed on a group of semiconductor wafers, sometimes referred to as a lot. For example, a process layer composed of a variety of materials may be formed above a wafer. Thereafter, a patterned layer of photoresist may be formed above the process layer using known photolithography techniques. Typically, an etch process is then performed on the process layer using the patterned layer of photoresist as a mask. This etching process results in formation of various features or objects in the process layer. Such features may be used for variety of purposes, e.g., in a gate electrode structure for transistors. The manufacturing tools within a semiconductor manufacturing facility typically communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which a manufacturing network is connected, thereby facilitating communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process.
FIG. 1 illustrates a typical semiconductor wafer 105. The wafer 105 typically includes a plurality of individual semiconductor die 155 arranged in a grid 150. Photolithography steps are typically performed by a stepper on approximately one to four die locations at a time, depending on the specific photomask employed. Photolithography steps are generally performed to form patterned layers of photoresist above one or more process layers that are to be patterned. The patterned photoresist layer can be used as a mask during etching processes, wet or dry, performed on the underlying layer or layers of material, e.g., a layer of polysilicon, metal or insulating material, to transfer the desired pattern to the under-lying layer. The patterned layer of photoresist is comprised of a plurality of features, e.g., line-type features or opening-type features that are to be replicated in an underlying process layer.
Turning now to FIG. 2, one example of a block diagram representation of a typical manufacturing process flow is illustrated. A manufacturing system prompts a first processing tool to perform a first process upon a semiconductor wafer 105 (block 210). A manufacturing data acquisition tool (e.g., a metrology tool) then analyzes at least some of the processed semiconductor wafers 105 (block 220). The metrology data acquired is then analyzed in a data analysis tool, e.g., a computer. The analyzed data can then be used to adjust various parameters related to manufacturing control of subsequent processes in order to reduce any effects of existing manufacturing errors (block 240). Once the manufacturing data analysis is performed, manufacturing data for feedback corrections is made available to the manufacturing system (block 250). The manufacturing system then uses the feedback data to perform corrections on subsequent processes performed on other semiconductor wafers 105 by a processing tool.
Generally, feedback data that is used to correct process deviations to reduce the effects of errors is acquired in an offline manner. The manufacturing data is then analyzed to produce possible feedback correction data to subsequent processing performed on a subsequent lot of semiconductor wafers 105. Utilizing the feedback method illustrated in FIG. 2, a coarse adjustment to the processing scheme is possible, feedback adjustments from one lot to another. Therefore, several semiconductor wafers 105 within a first lot may contain errors or imperfections that may not be present in a subsequent lot of semiconductor wafers 105, resulting in an inconsistent level of quality of manufactured semiconductor wafers 105. Furthermore, utilizing the prior art feedback scheme, errors occurring on a first few semiconductor wafers 105 within a lot may continue to propagate to the remaining semiconductor wafers 105 within the same lot.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one embodiment of the present invention, a method is provided for combining integrated and offline metrology data for process control. A process operation on a first semiconductor wafer within a first lot of semiconductor wafers is performed. Integrated metrology data from the first semiconductor wafer is acquired, the integrated metrology data comprising inline metrology data. A dynamic time process control based upon the integrated metrology data is performed, the dynamic time process control comprising a wafer-to-wafer feedback loop. A second semiconductor wafer (which may be one of a plurality of subsequently processed semiconductor wafers) within the first lot is processed based upon the dynamic time process. Offline metrology data from at least one of the first semiconductor wafer and the second semiconductor wafer from the lot is acquired. A constant time process control based upon the offline metrology data and the integrated metrology data is performed, the constant time comprising performing a lot-to-lot feedback process.
In another embodiment of the present invention, a system is provided for combining integrated and offline metrology data for process control. The system of the present invention comprises a process controller to perform a dynamic time process control and a constant time process control, the process controller being capable of: performing a process operation on a first semiconductor wafer within a first lot of semiconductor wafers; acquiring integrated metrology data from the first semiconductor wafer, the integrated metrology data comprising inline metrology data; performing the dynamic time process control based upon the integrated metrology data, the dynamic time process control comprising a wafer-to-wafer feedback loop; processing a second semiconductor wafer within the first lot based upon the dynamic time process; acquiring offline metrology data from at least one of the first semiconductor wafer and the second semiconductor wafer from the lot; and performing the constant time process control based upon the offline metrology data and the integrated metrology data, the constant time comprising performing a lot-to-lot feedback process. The system of the present invention also comprises: a metrology data storage unit operatively coupled to the process controller, the metrology data storage unit to receive the integrated metrology data and the offline metrology data; and an inline/offline metrology data integrating unit operatively coupled to the process controller and the metrology data storage unit, the inline/offline metrology data unit to combine the integrated metrology data with the offline metrology data for utilization in performing the dynamic time process control and the constant time process control.